This doesn't make sense on a lot of levels.
Intel not selling Sandy Bridge in numbers shouldn't make people run for AMD. AMD is worse than Intel's two generation old stuff; a Penryn is still faster than AMD stuff. Nehalem is way faster. They would go there.
What would this do to Intel's relationship with Dell? Would Dell be willing to damage the relationship with the premier maker, to get a low-end parts supplier? Would Dell's customers be OK with inferior products? Well, they have been, so maybe yes. But, they'd lose a lot of customers that want Intel, and Dell buying AMD would end their relationship with Intel. It would have to. How could Dell tell people to buy AMD when they themselves sell mostly Intel?
Also, Dell is only a cardboard box maker. They have never been a technology company, unless you consider new cardboard composites technology. They are allergic to innovation, and the expenses it entails. Since AMD doesn't make motherboards, it's really hard to see how this makes any sense at all. On top of all this, it would spell the end to ATI, since competitors would not want to buy from Dell.
Processors and GPUs need a lot of investment money. Dell buying AMD would lower, dramatically, market share because HP isn't going to want to buy from them, and other OEMs will be the same. It just makes no sense at all, on any level.
Dell buying Centaur, and the chipset business from VIA might be worth talking about. But, AMD makes no sense.